Building Beefy Gold Nuggets: The Geology Behind Earthquake Formation
When it comes to the formation of gold nuggets, earthquakes play a surprisingly crucial role. Recent research published in Nature Geoscience sheds light on the connection between seismic activity and the creation of these valuable mineral deposits. The study reveals how strain from earthquakes can stimulate the deposition of gold in quartz veins, ultimately leading to the formation of large nuggets. This groundbreaking discovery has significant implications for our understanding of how gold is concentrated in the Earth’s crust.
The Role of Quartz in Gold Mineralization
Quartz, a common mineral found in the Earth’s crust, possesses a unique property known as piezoelectricity. This means that when quartz is subjected to strain or pressure, it can generate an electrical voltage. During earthquakes, the intense pressure and movement of the Earth’s crust can cause quartz veins to undergo significant strain, leading to the generation of electrical charges. These voltages, in turn, can attract gold particles from passing fluids, resulting in the mineralization of gold within the quartz veins.
One of the lead researchers on the study, Christopher Voisey from Monash University, explains the significance of this process. He describes a scenario where a large gold nugget is found in the center of a quartz vein, with no apparent source for the gold around it. This mysterious occurrence has puzzled geologists for years, but the new findings provide a plausible explanation for how such nuggets are formed.
The Formation of Orogenic Gold Deposits
Much of the world’s gold is extracted from orogenic gold deposits, which are characterized by networks of quartz veins that contain significant amounts of gold. These deposits are typically formed deep underground, around six to 12 kilometers below the Earth’s surface. The process begins with earthquakes creating fractures in the rock, which are then filled with fluids carrying dissolved gold.
As these fluids infiltrate the fractures, they deposit quartz and gold, forming veins within the rock. Subsequent earthquakes further open up these fractures, allowing more fluids to flow in and deposit additional gold and quartz. Over time, this incremental process results in the formation of large, interconnected networks of gold-bearing veins.
While geologists have long understood how this process can lead to the formation of gold deposits, the mechanism by which gold becomes concentrated in large nuggets has remained elusive. The new research suggests that the piezoelectric properties of quartz play a key role in this concentration process, attracting gold particles and facilitating their aggregation into sizable nuggets.
The Experimental Evidence
To test their hypothesis, the researchers conducted experiments using quartz slabs immersed in solutions containing dissolved gold. By subjecting the slabs to simulated seismic activity, they were able to generate electrical voltages in the quartz, causing gold grains to aggregate on the surfaces of the slabs. This phenomenon was not observed in slabs that were not subjected to strain, highlighting the importance of earthquake-induced pressure in the mineralization process.
When a chunk of a gold-quartz vein was used in the experiment, the results were even more pronounced. The existing gold within the vein acted as a “lightning rod” for further gold deposition, attracting more particles and concentrating the mineralization in specific areas. This finding provides a compelling explanation for how gold nuggets can form within quartz veins, even in chemically inert environments.
In conclusion, the study offers a fascinating glimpse into the geological processes that govern the formation of gold nuggets. By elucidating the role of piezoelectricity in quartz veins during earthquakes, researchers have uncovered a crucial mechanism for the concentration of gold in the Earth’s crust. This discovery not only enhances our understanding of gold mineralization but also opens up new possibilities for the exploration and extraction of this precious metal in the future.
